Method for manufacturing a fiber reinforcement body for a metal matrix composite

ABSTRACT

A method and an apparatus for manufacturing a fiber reinforcement body which is to be incorporated into a metal matrix in a fabrication technique based on a molten metal infiltration process for producing a metal matrix composite material are disclosed herein. The method according to the invention comprises preparing at least two metal insert chills each having the shape of a spool or reel, forming windings of a yarn of reinforcing fibers on each of the two chills, and forming windings of the yarn around, and extending between the two chill members so as to connect them together. The apparatus of the invention comprises means for supporting the chill members in longitudinally spaced relation to each other, means for forming uniformly distributed windings of the yarn on each of the chills, and means for forming similar windings of the yarn around, and extending between the chills in a way so as to connect them together.

FIELD OF THE INVENTION

The present invention relates to a method of manufacturing a fiberreinforcement body which is placed in a mold cavity to be incorporatedas a part of the metal matrix in a fabrication technique based on moltenmetal infiltration, such as squeeze casting, an autoclave process, etc.,thereby reinforcing the resulting metal matrix composite (MMC) part. Theinvention also relates to an apparatus for performing the method. Morespecifically, it relates to a method and an apparatus for forming thefiber reinforcement body wherein a yarn of reinforcing fibers is firstwound on each of a plurality of spaced apart inserts or internal chills,each in the form of a reel and made of any easily-machinable metal, andthen around and between the chill members so as to connect themtogether.

BACKGROUND OF THE INVENTION

A fabrication technique based on molten metal infiltration casting forproducing metal matrix composites (MMC) and a technique for reinforcingsuch composites by use of fibers made of reinforcing materials, such asaluminium oxide, silicon carbide, silicon nitride, boron, graphite,etc., which are incorporated into the metal matrix are known in therelevant art. In the production of metal matrix composites thusreinforced by fibers, parts of various alloys containing from 30 to 60percent fibers by volume can be fabricated relatively easily. It isknown from the well-established rule of mixture that a high content ofsuch fibers can improve the mechanical and physical properties of thefiber-reinforced metal matrix composites.

For successfully reinforcing the metal matrix composite with fibers, itis very important that the reinforcement should have the right contentof fibers and be set rigidly at the right location in the cavity of thecasting mold. One example for achieving the desired rigidity of thefiber reinforcement is disclosed by Japanese Patent Publication No.56-111,565 of 1981, according to which reinforcing fiber bundles areimmersed in a volatile organic solvent and thereafter shaped into afiber reinforcement body having a form which suits the mold cavity inwhich it is to be placed. In a further known proposal disclosed byJapanese Patent Publication No. 56-66,368 of 1981, a yarn ofhigh-strength fibers is wound around an aluminium wire to make areinforcement string, and a number of such strings are shaped into areinforcement body having a form which substantially corresponds to thatof the casting to be produced.

However, these proposals have a serious disadvantage in that, becausethe fibers of the reinforcement body when placed in the mold cavity tendto be moved easily, they are very likely to be deflected from theirintended location within the cavity by the flow of molten metal as it isbeing injected into the cavity under pressure, with the result that thestrength of the resulting metal matrix composite is decreased, or partof the fibers may be exposed on the product surface. In addition,because fiber reinforcement bodies according to the prior art are madeby hand, the fibers cannot be practically arranged with the requireduniformity of distribution thereof within the body, and manufacturing ofreinforcement bodies on a mass production basis cannot be achieved.

SUMMARY OF THE INVENTION

It is an object of the present invention, therefore, to solve the aboveproblems by providing a method wherein fiber bundles can be wound andprepared in a continuous and orderly arrangement, desirably with the aidof a winder.

It is another object of the invention to provide an apparatus forperforming the method.

The above object is achieved by a method which comprises the steps ofpreparing at least two internal chill members each made of anyeasily-machinable metal and each preferably in the form of a spool orreel, forming uniformly distributed windings of a yarn of reinforcementfibers on the periphery of each such ring-shaped chill member, and thenforming similar windings of the yarn in the form of a belt extendingaround and between the spaced apart chill members so as to interconnectthem. If required, the interconnecting portion of the fibers extendingbetween the chill members can be reshaped into any desired form by usingmeans as will be described for reshaping and retaining the fibers.

Additionally, the present invention discloses an apparatus for carryingout the above method, which comprises means for supporting each of thechill members in spaced-apart relation, means for forming windings ofthe yarn of reinforcement fibers on the periphery of each chill member,and means for forming windings of the yarn around and extending betweenthe chill members so as to connect them together.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing a fiber reinforcement body made accordingto the present invention and placed in the cavity of a metal mold forcasting a connecting rod of an internal combustion engine by afabrication technique based on a molten metal infiltration process;

FIG. 2 is a side sectional view of FIG. 1;

FIG. 3 is a plan view, partly in section, of an embodiment of apparatusconstructed according to the invention;

FIG. 4 is a plan view of the apparatus of FIG. 3, showing the step ofthe method during which windings of reinforcement fibers are beingformed on the periphery of one internal chill mounted on the apparatus;

FIG. 5 is a plan view similar to FIG. 4, but showing the step in whichthe periphery of another chill is being wrapped with fiber windings;

FIG. 6 is a plan view of the apparatus, showing the step during theforming of windings of fibers in the form of a belt around, andextending between the two internal chills; and

FIG. 7 is a plan view showing the step wherein, after the fiber windingoperations have been completed, the fiber belt is being reshaped.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings wherein a preferred embodiment of thepresent invention is illustrated, reference numeral 1 in FIGS. 1 and 2designates a metal mold or die cooperating with its associated uppermold or cope 100 to form a cavity 2 therein which is so shaped in theillustrated embodiment as to cast a connecting rod of an internalcombustion engine by using a fluid metal infiltration process. A fiberreinforcement body 3 is accommodated and set within the mold cavity 2.The body 3 includes a pair of insert chills 6 and 7 made of aneasily-machinable metal, such as an aluminium or a stainless steel, thepurpose of which is well known in the art, each preferably in the formof a ring or reel. The chills 6 and 7 are disposed at respectivelocations within the cavity 2 corresponding to the journals at the largeand small ends of the connecting rod, respectively. Each chill memberhas wrapped on its periphery a uniformly distributed series of windingsof a yarn 8 across its width, forming a bundle of fibers of anyreinforcing material, such as aluminium oxide, silicon carbide, siliconnitride, boron, graphite, or other yarn fiber material, and the twochill members 6, 7 are connected by additional and similarly distributedwindings of the yarn 8 forming an endless belt running therearound andextending therebetween. As most clearly seen in FIG. 1, two metalmembers 10, 10 each bent into a rectangular shape are attached to theintermediate belt portion to reshape the belt portion into a formcommensurate with the portion of the cavity 2 corresponding to the rodportion 9 of the connecting rod, and to maintain that form. As shown inFIG. 2, the mold cavity 2 has upward projections 11 and 12 formed atrespective locations to receive and fit into the central openings orbores of the chill members 6 and 7, respectively, so that thereinforcement body 3 when set into the mold cavity 2 may be held in thecavity 2 securely, with its yarn windings extending along the rodportion 9, and under proper tension.

The chill members 6, 7 are formed at the cylindrical portions thereofwith a plurality of perforations 13, as shown in FIG. 2 and also in FIG.4, to permit thorough infiltration of molten metal in the mold cavity 2when the fluid metal, which is poured through a sprue hole 101 formed inthe cope 100, is squeezed to be infiltrated throughout the cavity 2,under pressure exerted by a plunger 102.

Reference is now made to FIGS. 3 to 7 which illustrate an apparatus ofthe invention for making the above-described fiber reinforcement body 3,and the method according to the invention by which the body is madeusing the apparatus.

The apparatus comprises a winding device which is designated generallyby reference numeral 14. The winder 14 includes an extensible armassembly 16 fixed at its center on the end of a rotatable main shaft 15,the arm assembly 16 being shown in its lengthened or extended state inFIG. 3, as will be explained. The arm assembly 16 further includes amain arm portion 17 which is fixed to the shaft 15, and a movable armportion 18 which is slidably fastened to an end of the arm portion 17 bymeans of a bolt 19 passed through an elongated hole in such a way thatthe arm portion 18, when unfastened, may be moved toward and away fromthe the main arm portion 17. At the respective ends of the arm assembly16, i.e., on the free end of the arm portion 17 and on the arm portion18, are supported rotatable shafts 20, 21 in longitudinally spaced-apartrelation. The shafts 20, 21 have respective guide rollers 22, 23,including respective projecting portions 22a, 23a, carried on the endsthereof, on the right hand side as viewed in the drawing, for receivingthereon the chill members 6, 7, respectively. In addition, the shafts22, 23 carry respective rubber rollers 24, 25 on their opposite ends,for receiving power by which the shafts 20, 21 are respectively rotated.

The rubber rollers 24, 25, and hence the guide rollers 22, 23 carried onthe common shafts 20, 21, are driven one at a time by a shiftablefriction wheel 26 which, when shifted to its operative position as shownby full lines in FIGS. 3 to 5, is brought into frictional drivingcontact with either of the rubber rollers 24, 25 which, at the time, ispositioned adjacent thereto, as will be seen. The friction wheel 26 maybe shifted to its inoperative position, as shown by phantom lines inFIGS. 3 to 5, in which it is out of contact with the adjacent rubberroller. Reference numeral 27 designates a yarn guide which operates inconjunction with the rotation of the friction wheel 26 when in itsoperative position, and in conjunction with the rotation of the mainshaft 15, to reciprocate laterally over a distance corresponding to thewinding width on the periphery of the chill members 6, 7, for guidingand depositing the yarn 8 on the chill members as the yarn is paid offfrom its source (not shown). Thus, the yarn is wound evenly on andacross the peripheries of the chill members 6, 7 to form orderlybuilt-up windings.

The chill members 6, 7 are detachably mounted on their correspondingguide rollers 22, 23 by means of wing head bolts 32 and washers 31 whichpress them against the laterally facing surfaces of the rollers, asshown. The central openings or bores of the chill members arerespectively received on the projections 22a, 23a. Thus, the chills 6, 7are held in longitudinally spaced-apart relation with respect to eachother.

A retractable stop pin 29 is provided which cooperates with itsassociated holes 30, 30 formed at the outermost ends of the arm assembly16, respectively, for holding the arm 16 stationary during winding ofthe yarn 8 on either of the chill members. This pin 29 is disengagedfrom either of the holes 30 when the entire arm assembly 16 is rotatedby the main shaft 15, as will be seen.

In operation of the apparatus thus constructed, firstly, the leading endof a strand of the yarn 8 as supplied from the source (not shown) ispassed through the yarn guide 27 and is attached on the periphery of thechill member 7. Then, the friction wheel 26 is brought into contact withthe rubber roller 25, and rotated to drive the shaft 21. The chillmember 7 carried on the same shaft 21 is thus caused to rotate and,simultaneously, the yarn guide 27 starts moving reciprocatingly, inlateral direction, in controlled relation with the rotation of the shaft21. Accordingly, the fiber yarn 8 is wound in an evenly built-uparrangement onto the periphery of the chill member 7, as shown in FIG.4, because of the reciprocating motion of the yarn guide 27 in unisonwith the rotation of the chill member 7. The amount or volume of thefiber winding to be formed on the chill member may be ascertained byusing any known device for counting the number of rotations of the shaft21, and hence the number of turns of the yarn 8 on the member. It may beso arranged that the drive for the friction wheel 26 is stoppedautomatically when a predetermined volume of the winding is formed onthe chill member.

After the chill member 7 has been wrapped with the predeterminedquantity of fibers, the yarn 8 is cut off and the friction wheel 26 isshifted to its inoperative position as shown by phantom lines in FIG. 4.With the friction wheel 26 held in its inoperative position, the mainshaft 15 is turned 180° to bring the the other chill member 6 to thewinding position adjacent to the yarn guide 27 and friction wheel 26,and the friction roller 26 is again shifted to its operative positionwhere it contacts the rubber roller 24, as shown in FIG. 5. By attachingthe cut leading end of the yarn 8 passed through the yarn guide 27 tothe chill member 6, and then driving the shaft 20 by the friction wheel26, by way of the rubber roller 24 in contact therewith, an evenbuild-up of yarn windings is formed on the periphery of the chill member6 in manner similar to that in which the yarn was wound on the chillmember 7.

After the winding of the reinforcing yarn fiber on both chill members 6,7 has been completed, the friction wheel 26 is moved to its inoperativeposition, and the main shaft 15 is driven by means, not shown, so as torotate in the direction indicated by the arrow in FIG. 6, a directionwhich will not cause unwinding of the yarn already formed on the chillmember 6. Because the yarn guide 27 is reciprocated in timed relation tothe rotation of the main shaft 15, the fiber bundle 8 is wound aroundand between both chill members 6 and 7 in an even manner, in the form ofan endless belt that interconnects the two chill members. FIG. 6 showsan intermediate stage of such winding operation, before a complete beltof fibers has been formed.

The rotation of the main shaft 15 is stopped as the winding of the yarn8 between the chill members 6, 7 is completed, and the bolt 19 isloosened to permit movement of the arm portion 18. Then, the two metalmembers 10 are attached to the fiber belt at respective intermediatelocations between the chill members 6, 7, as shown, while sliding themgradually toward each other. In the illustrated embodiment, the metalmembers 10, 10 are provided on the belt portions at such locations andin such a way that the resulting shape of the intermediate portion ofthe fiber reinforcement body 3 substantially corresponds to the shape ofthe rod portion 9 of the mold cavity 2. Furthermore, the movable armportion 18 is so arranged that the arm assembly 16 is fully contracted,or assumes its shortest size as shown in FIG. 7, when the attachment ofthe metal members 10, 10 is completed.

Though the reinforcement body 3 thus formed may be separated from theguide rollers 22, 23 merely by removing the bolts 32 and their washers31, it is desirable that the body should be removed from the winder 14without disturbing the orderly arrangement of the fiber windings.Accordingly, a jig 28, which is designed specifically to conform to theshape of the reinforcement body as shown in FIG. 7, may be usedadvantageously for the purposes of maintaining the desired tension ofthe fibers along the intermediate portion of the body 3, as well as foravoiding the abovesaid disturbance of the fiber windings. Furthermore,this jig 28 may be used as a holder for the fiber reinforcement body 3when setting it into the mold cavity 2. That is, as seen in FIG. 7, thejig 28 has respective cylindrically shaped portions 28a, 28b whichproject and fit snugly into the respective bores of the chill members 6and 7 while the fully formed body 3 is still mounted on the winder 14,to maintain their spaced relation. The body 3 is then removed from thesimilar projections 22a, 23a on the winder rollers 22, 23, with the jig28 connected thereto, and is placed within the mold cavity 2 with thebores of its chills 6, 7 received on the similarly shaped moldprojections 11 and 12 (FIG. 2). The jig 28 is then removed, and the moldis closed.

As it is now apparent from the foregoing, the use of the method orapparatus of the invention, according to which any desired quantity ofreinforcement fibers can be wound on chill members in an orderlyarrangement, can contribute to the improvement of properties of thefiber-reinforced metal matrix composites to be produced by fluid metalinfiltration casting processes, and also makes possible mass-productionof the fiber reinforcement bodies with easy maintenance of theirintended quality.

While the invention has been illustrated and described with reference tospecific embodiments, it is to be understood that various modificationsin the details of the method or the apparatus may be made withoutdeparting from the spirit and scope of the invention.

What is claimed is:
 1. A method of preparing a fiber reinforcement bodyand mounting the same within a mold for use in a molten metalinfiltration casting process for reinforcing the metal matrix compositearticle to be produced thereby, said method comprising providing atleast two chill members, supporting said chill members in spaced-apartrelation to each other, forming uniformly distributed windings of a yarnof fibers made of a reinforcing material on and along the peripheralwidth of each of said chill members, forming other uniformly distributedwindings of said yarn in the form of a belt extending around and betweensaid chill members and superposed on the first said windings so as toconnect said chill members together while maintaining their saidspaced-apart relation, thereby forming said fiber reinforcement body,and placing said reinforement body within an injection mold whilemaintaining said spaced-apart relation of said chill members, saidplacing step comprising attaching a jig to all of said chill memberswhile supported in their said spaced-apart relation, and then moving andpositioning said jig to place said reinforcement body within said mold,all of said chill members being fitted on respective mold receivingmeans to retain their said spaced-apart relation when placed in saidmold and said jig is removed.
 2. A method according to claim 1, whereinsaid windings on each said chill member are formed by attaching an endof said yarn to a location on the periphery of said chill member andspinning the chill member to wind said yarn thereon while guiding theyarn to wind and deposit said yarn evenly on and across said chillmember periphery.
 3. A method according to claim 2, wherein said yarn isguided by feeding said yarn through guide means, and moving said guidemeans reciprocatingly and parallel to the axis of said spinning of thechill member along its said periphery over a distance substantiallycorresponding to the peripheral width of the member.
 4. A methodaccording to claim 1, wherein said step of forming said other windingsof said yarn around and between said chill members comprises spinningall of said chill members together about a common axis while maintainingtheir said spaced apart relation and while said yarn is attached to oneof said chill members to wind and deposit said yarn evenly around andbetween the peripheries of all of said chill members.
 5. A methodaccording to claim 4, wherein said yarn is guided by feeding said yarnthrough guide means, and moving said guide means reciprocatingly andparallel to the axis of said spinning of all of said chill members alongtheir peripheries.
 6. A method according to claim 5, wherein said guidemeans is moved reciprocatingly over a distance substantiallycorresponding to the peripheral width of at least one of said chillmembers.
 7. A method according to claim 1, which further comprisesattaching a retainer on and between strand portions of said belt ofother windings to change their spacing distance and thereby reshape saidother windings at a location between said chill members.